Tuning of the structural, elastic, electronic, optical, and thermodynamic properties of TlCrX2 (X = S, Se) for optoelectronic and electronic devices

Abstract

For the first time, first-principles investigations using density functional theory (DFT) were thoroughly conducted on the structural, mechanical, optical, anisotropic, thermodynamic and electronic properties of TlCrX₂ (X = S, Se) materials. The mechanical stability of both compounds is confirmed as their elastic constants satisfy the Born criteria. The bulk modulus, Poisson's ratio and shear modulus have been utilized to investigate the mechanical stability of this compound. The comparisons of the elastic moduli show a significant correlation with previously obtained experimental data. Notably, TlCrSe₂ transitions from brittle to ductile when Se is substituted with S, improving its machinability for industrial uses. TlCrSe₂ is characterized by its softness, ductility, high machinability, and exceptional dry lubricity. Additionally, these materials display anisotropy. The melting temperature, phonon thermal conductivity, and Debye temperature of TlCrX₂ (X = S, Se) are low, while the compound shows a moderate Grüneisen parameter. TlCrX₂ compounds exhibit moderate Debye temperatures, low melting points, and Grüneisen parameters, indicating their potential use in thermal barrier coatings. In addition, an in-depth optical evaluation reveals that these compounds hold promise for use in electronic and optoelectronic devices. Both materials exhibit a high refractive index at low energy levels, including the visible spectrum, and uniform reflectivity across a wide range of photon energies. TlCrX₂ (X = S, Se) exhibit high UV absorption, making them excellent candidates for UV-related applications, such as surgical equipment disinfection, photovoltaic materials for X-ray phosphors, space technology and solid-state LED lighting. Their high reflectivity in the visible range suggests potential as efficient solar reflectors to minimize solar heating, while low reflectivity at higher energies (above 15 eV) and a high refractive index at low photon energies highlight their suitability for optoelectronic devices, including LEDs. These properties underscore their versatility for advanced optical and electronic applications.